[Taxacom] Propagation of invasive species definitions

[Curtis Clark]

  On 9/11/2010 6:26 AM, Frederick W. Schueler wrote:
> * okay, the question is, what is invaded? At least in Canada, again, 
> in the late 1980s and early 1990s, the original idea was that it was 
> habitats otherwise undisturbed by people that are invaded, so that 
> "invasive" species don't include those that malacologists call 
> synanthropic, however abundant these may be. The metaphor was that the 
> invasive species marches into the woods or wetlands on its own, like 
> an invading army conquering territory, rather than being set up by 
> overt human creation of its habitat.

California has its share of "invasive species" by any definition, and 
certainly ecologists commonly distinguish those that move into intact 
habitat from those that are restricted to human disturbance. At issue, 
though, is the scope and intensity of human disturbance. There is clear 
evidence that nitrogen precipitated from air pollution allows many 
invasive grasses to expand into habitat in which they would otherwise 
not be competitive. So one could realistically say that in some parts of 
California, there are no habitats that are not impacted by human 
disturbance.


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Curtis Clark                  http://www.csupomona.edu/~jcclark/
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